(+)-1,4-Dihydro-7-[(3 S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid is known for its anti-tumor activity (see, Tsuzuki et al., J. Med. Chem., 47:2097-2106, 2004 and Tomita et al., J. Med. Chem., 45: 5564-5575, 2002). Treatment of the following cancers with (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid has been proposed in the literature: bladder cancer, breast cancer, cervical cancer, colon cancer, esophageal cancer, head and neck cancer, liver cancer, lung cancer, melanoma, myeloma, neuroblastoma, ovarian cancer, pancreatic cancer, prostate cancer, renal cancer, sarcoma, skin cancer, stomach cancer, testicular cancer, thyroid cancer and uterine cancer. Various dosing regimens for the use of this compound have been reported, for example, see, U.S. Patent Application Pub. Nos. 2005-0203120; 2005-0215583 and 2006-0025437 and International Application No. PCT/US2006/034699, which are incorporated herein by reference in their entirety.